How Do I Find the Point of Inflection in a Cubic Graph?

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Discussion Overview

The discussion revolves around finding the point of inflection in a cubic graph, focusing on curve sketching techniques and the role of derivatives in identifying such points. The scope includes conceptual understanding and mathematical reasoning related to derivatives.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant suggests using the definition that the second derivative is zero at the inflection point and that the first derivative changes sign there.
  • Another participant seeks clarification on what is meant by "changes sign," expressing understanding of the gradient and concavity but requesting further elaboration.
  • A later reply corrects the initial statement, clarifying that it is the second derivative that changes sign at the inflection point, indicating a change in concavity.
  • One participant inquires about definitions for convex and concave, indicating a desire for deeper understanding of these concepts.

Areas of Agreement / Disagreement

The discussion shows some agreement on the role of the second derivative in identifying inflection points, but there is a lack of consensus on the definitions and implications of convexity and concavity.

Contextual Notes

Participants express varying levels of understanding regarding the definitions of convex and concave, and there are unresolved aspects related to the implications of sign changes in derivatives.

garyljc
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Hey guys ,
I'm currently learning curve sketching
and i was thinking ... what would be the best approach towards finding the point of inflection in a cubic graph . Any suggestions ?
Thanks
 
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?? Using the definition- that the second derivative is 0 and the first derivative changes sign there.
 
What do you mean by changes sign ?
I do understand that the sign change in the first derivative means the gradient
the second derivative means whether the curve is concave or convex ...
that's all i know about the signs so far..
do you mind elaborating more ?
thanks
 
My mistake, I meant that the second derivative changes sign there: is positive on one side of the inflection point and negative on the other. Yes, second derivative positive means the curve is "convex" upward and second derivative negative means the curve is "convex" downward ("concave" upward). At an inflection point the concavity changes.
 
i was wondering if there's an definition for convex and concave ... is there ?
 

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